A cricketer can throw a ball to a maximum horizontal distance of 100 m. The speed with which he throws the ball is (to the nearest integer)

• 30 ms^-1

• 42 ms^-1

• 32 ms^-1

• 35 ms^-1

A box whose mass is 5 kg lies on a spring balance inside a lift. The lift starts to ascend with an acceleration of 2 ms^-2. The reading of the machine or balance is (g = 10 ms^-2)

• 50 kg

• zero

• 49 kg

• 60 kg

A man runs towards a mirror at a speed 15 m/s. The speed of the image relative to the man is

• 15 ms^-1

• 30 ms^-1

• 35 ms^-1

• 20 ms^-1

A student is standing at a distance of 50 metre from the bus. As soon as the bus begins its motion with an acceleration of 1 ms^-2,  the student starts running towards the bus with a uniform velocity u. Assuming the motion to be along a straight road, the minimum value of u, so that the student is able to catch the bus is

• 8 ms^-1

• 5 ms^-1

• 12 ms^-1

• 10 ms^-1

A bullet moving with a speed of 100 ms^-1 can just penetrate two planks of equal thickness. Then, the number of such planks penetrated by the same bullet when the speed is doubled will be

• 6

• 10

• 4

• 8

A balloon is rising vertically up with a velocity of 29 ms^-1 .A stone is dropped from it and it reaches the ground in 10 seconds. The height of the balloon when the stone was dropped from it is (g = 9.8ms^-1)

• 400 m

• 150 m

• 100 m

• 200 m

From the top of a tower of two stones, whose masses are in the ratio 1 : 2 are thrown on straight up with an initial speed u and the second straight down with the same speed u. Then neglecting air resistance

• the heavier stone hits the ground with a higher speed

• the lighter stone hits the ground with a higher speed

• both the stones will have the same speed when they hit the ground

• the speed can't be determined with the gven data

A cyclist starts from the centre O of a circular park ofradius 1 km, reaches the edge P of the park, then cycles along the circumference and returns to the centre along QO as shown in the figure. If the round trip takes 10 mm, the net displacement and average speed of the cyclist (in metre and kilometre per hour) are

• 0, 1

• $\frac{\mathrm{\pi } + 4}{2}, 0$

• $21.4, \frac{\mathrm{\pi } + 4}{2}$

• 0, 21.4

79.

For ordinary terrestrial experiments, the observer in an inertial frame in the following cases is

• a child revolving in a giant wheel

• a driver in a sports car moving with a constant high speed of 200 kmh^-1 on a straight rod

• the pilot of an aeroplane which is taking off

• a cyclist negotiating a sharp curve

A body of mass m moving along a straight line covers half the distance with a speed of 2ms^-1. The remaining half of the distance is covered in two equal time intervals with a speed of 3 ms^-1 and 5 ms^-1 respectively. The average speed of the particle for the entire journey is

• $\frac{3}{8} {\mathrm{ms}}^{-1}$

• $\frac{8}{3} {\mathrm{ms}}^{-1}$

• $\frac{4}{3} {\mathrm{ms}}^{-1}$

• $\frac{16}{3} {\mathrm{ms}}^{-1}$